In my early 20s I started messing with opal rough, and have continued now for many years. When I was young and broke, I worked opal in extremely low tech ways.
I just want to add to Michael post. I use his method to teach any one
that want to cut and polish any stones and who do not want to invest
in lapidary equipment. I have not found a stone that it does not work
on, but I believe it is one of the best way to cut opals, if your
cutting them for yourself and not mass cutting.
I also teach to just use a grinder from the hardware store for
grinding nearly every stone, including opal, to shape before going to
the sandpaper. YES, a water system must be used, I have my way of
doing this, but nearly everyone can figure out a way to put some sort
of water drip system on the wheels for safety and for keeping the
stones cool. Wear a good dust mask too, if you wish, or for sure if
you smoke.
To put a good polish on opal, and even chip inlay, I teach use a
piece of leather (A belt blank from a leather store is great, but any
unfinished leather piece is ok.) to polish. It is so simple that it
really upsets the students that have thousands of dollars in equipment
at home. Especially those that have cut a lot of opal, because it does
not have any chance of heating the opal, or putting a “egg shell”
finish on it and other softer stones. It works great with jade too.
Just soak the leather in water for about five minutes, then wet and
dip you finger in Linde A (a polish compound that is available from
nearly every lapidary supplier) and apply it to the leather. If your
afraid of getting stuff on your fingers, wear a rubber glove, no
problem. Use the smooth side, not the suede side. I am not that
familiar with leather terms, and do not care to learn, but there is a
smooth side and rough side, use the smooth side. It is a powder and
you should add enough to form a light paste on the leather.
Then just take you dopped stone and start rubbing it back and forth.
You will be amazed at how fast this method works. I thought that it
would take forever, when I first came up with it. The first time I
tried it, was actually during a class for my silver students. I told
them it was an experiment, and that it would most likely take a lot of
time, but better than spending hundreds for a lapidary unit if they
were not seriously interested in lapidary. I told them check with me
as they progressed to a polish, if there was a polish. In just a few
minutes, less than five, one student brought up their opal. I said,
“No you will need to work on it longer than that!”. She said, “Well,
just look at it!” I was shocked to see one of the best polishes on
opal than I have seen with any ones method and thousands of dollars
worth of equipment.
Give it a try, it will only cost you about $8.00 for the Linde A and
about $2.00 for the leather! I have not tried tin oxide, but I bet it
will do the same. My students have had great success with opal,
malachite, turquoise, petrified wood, dinosaur bone, sodalite, lapis
(great polish!), blue lace agate, tiger’s eye, and leaverite.
Leaverite is those stones you find that you should just leave right
where you find it! But they had fun cutting them.